Liwei Lin (Advisor)

Research Advised by Professor Liwei Lin

Lin Group:  List of Projects | List of Researchers

Rapid Genotypic Antibiotic Susceptibility Test Using CRISPR-Cas12a for Urinary Tract Infection

Juhong Chen
Fuguo Jiang
Chao-Wei Huang
Liwei Lin
2020

The current clinical protocol to conduct a bacterial antibiotic susceptibility test (AST) requires at least 18 hours, and cannot be accomplished during a single visit for patients. Here, a new method based on the technique of CRISPR-Cas12a is utilized to accomplish a bacterial genotypic AST within one hour with good accuracy. Two amplification approaches are employed and compared: (1) enriching the bacterial concentration by culturing in growth media; and (2) amplifying target DNA from raw samples by recombinase polymerase amplification (RPA). The results show that CRISPR combined with RPA...

Finger-Powered Fluidic Actuation and Mixing via MultiJet 3D Printing

Eric Sweet
Rudra Mehta
Yifan Xu
Ryan Jew
Rachel Lin
Liwei Lin
2020

Additive manufacturing, or three-dimensional (3D) printing, has garnered significant interest in recent years towards the fabrication of sub-millimeter scale devices for an ever-widening array of chemical, biological and biomedical applications. Conventional 3D printed fluidic systems, however, still necessitate the use of non-portable, high-powered external off-chip sources of fluidic actuation, such as electro-mechanical pumps and complex pressure-driven controllers, thus limiting their scope towards point-of-need applications. This work proposes entirely 3D printed sources of human-...

3D Microfluidic Concentration Gradient Generator for Combination Antimicrobial Susceptibility Testing

Eric Sweet
Brenda Yang
Joshua Chen
Reed Vickerman
Yujui Lin
Alison Long
Eric Jacobs
Tinglin Wu
Camille Mercier
Ryan Jew
Yash Attal
Siyang Liu
Andrew Chang
Liwei Lin
2020

Microfluidic concentration gradient generators (µ-CGGs) have been utilized to identify optimal drug compositions through antimicrobial susceptibility testing (AST) for the treatment of antimicrobial-resistant (AMR) infections. Conventional µ-CGGs fabricated via photolithography-based micromachining processes, however, are fundamentally limited to two-dimensional fluidic routing, such that only two distinct antimicrobial drugs can be tested at once. This work addresses this limitation by employing Multijet-3D printed microchannel networks capable of fluidic routing in three dimensions to...

High-Aspect-Ratio Three-Dimensional Electrospinning via a Tip Guiding Electrode

Gaofeng Zheng
Jiaxin Jiang
Xiang Wang
Wenwang Li
Zhaojie Yu
Liwei Lin
2021

Electrospinning setup with a sharp tip guiding electrode has been designed for high-aspect-ratio three-dimensional (3D) electrospinning by enhancing the electrical field strength to guide nanofibers toward designated paths layer by layer. This setup helps to deposit nanofibers under a steady charge transfer process and overcomes the electrical interferences. The polymer jet via the electrohydrodynamic process has been used to direct-write ordered, 3D structures with the aspect-ratio (height/width) up to 25 for various patterns, such as rectangular grids and five-point stars....

Electrohydrodynamic 3D Printing of Orderly Carbon/Nickel Composite Network as Supercapacitor Electrodes

Bing Zhang
Jiangkang He
Gaofeng Zheng
Yuanyuan Huang
Chaohung Wang
Peisheng He
Fanping Sui
Lingchua Mueng
Liwei Lin
2021

Electrohydrodynamic (EHD) 3D printing of carbon-based materials in the form of orderly networks can have various applications. In this work, microscale carbon/nickel (C-Ni) composite electrodes with controlled porosity have been utilized in electrochemical energy storage of supercapacitors. Polyacrylonitrile (PAN) was chosen as the basic material for its excellent carbonization performance and EHD printing property. Nickel nitrate (Ni(NO3)2) was incorporated to form Ni nanoparticles which can improve the conductivity and the capacitance performance of the electrode. Well-aligned PAN-Ni(NO3...

Electrically Adaptive and Shape-Changeable Invertible Microlens

Jin Woo Bae
Dong-Soo Choi
In-Ho Yun
Dong-Heon Han
Seung Ju Oh
Tae-Hoon Kim
Jeong Ho Cho
Liwei Lin
Sang-Youn Kim
2021

Existing soft actuators for adaptive microlenses suffer from high required input voltage, optical loss, liquid loss, and the need for assistant systems. In this study, we fabricate a polyvinyl chloride-based gel using a new synergistic plasticization method to achieve simultaneously a high optical transparency and an ultrasoft rubber-like elastic behavior with a large voltage-induced deformation under a weak electric field. By compressing the smooth gel between two sets of annular electrodes, a self-contained biconvex microlens is realized that is capable of considerable shape changes in...

A 36-Channel Auto-Calibrated Front-End ASIC for a pMUT-Based Miniaturized 3-D Ultrasound System

Jihee Lee
Kyoung-Rog Lee
Benjamin E. Eovino
Jeong Hoan Park
Luna Yue Liang
Liwei Lin
Hoi-Jun Yoo
Jerald Yoo
2021

We present an area- and power-efficient application-specific integrated circuit (ASIC) for a miniaturized 3-D ultrasound system. The ASIC is designed to transmit pulse and receive echo through a 36-channel 2-D piezoelectric Micromachined Ultrasound Transducer (pMUT) array. The 36-channel ASIC integrates a transmitter (TX), a receiver (RX), and an analog-to-digital converter (ADC) within the 250-μm pitch channel while consuming low-power and supporting calibration to compensate for the process variation of the pMUT. The charge-recycling high-voltage TX (CRHV-TX) in standard CMOS...

Improved Ring-Down Time and Axial Resolutions of PMUTs via Phase-Shift Excitation Scheme

Sedat Pala
Zhichun Shao
Yande Peng
Liwei Lin
2021

We have proposed a phase-shift cancellation scheme to reduce the ring down period of ultrasonic transducers and increase axial resolutions. A piezoelectric micromachined ultrasonic transducer (pMUT) consisting of 80 elements with circular diaphragms of 415 μm in radius made of 2 μm-thick AlN layer has a measured resonant frequency of 160 kHz. The ring down period is minimized by emitting ten pulses followed by six additional pulses with a 180° phase difference. Results show the ring down period is shortened by 13% and 7.5% for a single element and the 80-element array, respectively. In...

Ultrasound-Induced Haptic Sensations via PMUTs

Sedat Pala
Zhichun Shao
Yande Peng
Liwei Lin
2021

This work presents the sense of touch via non-contact ultrasonic waves by a dual-electrode bimorph piezoelectric micromachined transducer (pMUT) array. The prototype device has 12×12 elements with circular diaphragms of 415μm in radius made of 2μm-thick AlN. They are fabricated by a CMOS compatible micromachining process resulting a resonant frequency at 109.4kHz. Experimentally, a best haptic sensation on human fingers is found when emitting high frequency ultrasonic waves to emulate 100Hz signals by means of pulse width modulation with a 50% duty cycle. Strong haptic sensations are...